Marcus-type driving force correlations reveal the mechanism of proton-coupled electron transfer for phenols and [Ru(bpy)(3)](3+) in water at low pH
2016 (English)In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 7, no 7, 4607-4612 p.Article in journal (Refereed) PublishedText
Proton-coupled electron transfer (PCET) from tyrosine and other phenol derivatives in water is an important elementary reaction in chemistry and biology. We examined PCET between a series of phenol derivatives and photogenerated [Ru(bpy)3](3+) in low pH (<= 4) water using the laser flash-quench technique. From an analysis of the kinetic data using a Marcus-type free energy relationship, we propose that our model system follows a stepwise electron transfer-proton transfer (ETPT) pathway with a pH independent rate constant at low pH in water. This is in contrast to the concerted or proton-first (PTET) mechanisms that often dominate at higher pH and/or with buffers as primary proton acceptors. The stepwise mechanism remains competitive despite a significant change in the pK(a) and redox potential of the phenols which leads to a span of rate constants from 1 x 10(5) to 2 x 10(9) M (1) s (1). These results support our previous studies which revealed separate mechanistic regions for PCET reactions and also assigned phenol oxidation by [Ru(bpy)(3)](3+) at low pH to a stepwise PCET mechanism.
Place, publisher, year, edition, pages
2016. Vol. 7, no 7, 4607-4612 p.
IdentifiersURN: urn:nbn:se:uu:diva-300099DOI: 10.1039/c6sc00597gISI: 000378715000079OAI: oai:DiVA.org:uu-300099DiVA: diva2:950821
FunderSwedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg Foundation